Features:
1. Display a given currency symbol, default value is null.
2. Display a thousand separator, this can be any character including blank space (' ') default value is ",".
3. Force decimal precision to display all decimals from "decimalPrecision" property.

Notes:

If you set thousandSeparator config option to "." automatically decimalSeparator will be set to "," unless you also set decimalSeparator explicitly.
I didn't remove the trigger so you can still click up and down to increase or decrease the value. It will be nice to know the opinions of this one.

I tried to use Ext.util.Format but it doesn't allow to apply all the options the extension provide, so i still use my own function to format the value. One property that is missing from the extension is "currencyAtEnd" requested before, i couldn't add it today.
Full size image of combinations can be found inside the zip file.

Thanks for the extension! I found it to be extremely helpful to me. I am in the process of developing a payroll processing utility and this extension is exactly what I needed to perform these types of functions. You did a great job coding this, it performs flawlessly!

OK, I think I figured out a way to get this to submit the "raw" (i.e. unformatted, numeric-only) value. And I think you were on the right track with processRawValue, brittongr. At least it appears to be working for me. Changes to the source (just the one function override) from the zip file are shown below in bold:

I haven't tested extensively (i.e. if there are implications to overriding this beyond simply what we're trying to achieve). But at least for me, this makes the NumericField fully usable for our ExtJS 4.x application. Thanks for taking the initiative on creating something that should have really been given out-of-the-box.

Thanks for the extension! I found it to be extremely helpful to me. I am in the process of developing a payroll processing utility and this extension is exactly what I needed to perform these types of functions. You did a great job coding this, it performs flawlessly!